Access control for elements in a database object

ABSTRACT

A system for controlling access to elements in a database object are provided. The system provides for receiving a request from a user to access the database object, determining whether an access restriction is imposed on the database object, and controlling access to the elements in the database object by the user based on the access restriction. The access restriction specifies one or more users to which the access restriction is applicable, defines a dynamic condition the one or more users must satisfy in order to access the database object, and identifies one or more of the elements in the database object accessible to the one or more users when the dynamic condition is satisfied.

CROSS-REFERENCE TO RELATED APPLICATIONS

Under 35 USC §120, this application is a continuation application andclaims the benefit of priority to U.S. patent application Ser. No.11/299,857, filed Dec. 12, 2005, entitled “Access Control for Elementsin a Database Object,” which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to database management systems.More particularly, the present invention is directed to controllingaccess to elements in a database object.

BACKGROUND OF THE INVENTION

In a Database Management System (DBMS), data is stored in tables made upof records (e.g., rows) having one or more fields (e.g., columns). Aview is a logical construct imposed over a table and is defined bymetadata in the DBMS known as a view definition. The view definitioncontains mappings to one or more rows and columns in one or more tablesstored in a database. Tables and views are considered to be databaseobjects.

Fine-Grained Access Control (FGAC) is a mechanism by which the DBMScontrols access to database object records and/or fields based on theidentity of the user attempting to access the database object. FGACcomplements the traditional Discretionary Access Control (DAC)implemented by many DBMS by allowing the DBMS to enforce two levels ofaccess control: DAC is enforced at the object level (e.g., does the userhave the right to access that table?) and FGAC is enforced at theelement level (e.g., does the user have the right to access that row orcolumn?).

Traditional methods of implementing FGAC within DBMS have relied uponthe use of views. A view can be used to alter or restrict the data seenby a user using the view to access the underlying table(s). Views,however, have a number of shortcomings. For example, when the number ofdifferent restrictions is numerous, view definitions may become quitecomplex in an effort to incorporate all of the restrictions in one view,which strains system limits and makes maintenance of the view difficult.

Additionally, if a large number of simple views are desired, e.g., eachone implementing a unique view of a table based on the restrictions fora specific set of users, the routing of user requests becomes difficultwith the solution often being resolved within the database applicationrather than the DBMS. Furthermore, a user may be able to bypass the FGACimplemented through the views by accessing the base tables directly.

Another known implementation of FGAC is the use of user attributes tomodify queries by adding predicates into the queries. A predicate is acondition that must be satisfied for the DBMS to return a value. In thisapproach, the user attributes (e.g., user identifier) are comparedagainst a security policy defined within a procedure provided by theuser on a table or view to make decisions regarding access to data. Thisapproach allows row restrictions, traditionally handled by views, to bedynamically added to queries without requiring application modification.

One drawback of the query modification approach is that it only allowsthe DBMS to control access at the row-level. Views still have to be usedto control access at the column-level. Additionally, the approachrequires user programming of a strictly defined “predicate producing”procedure in order to implement a security policy. Moreover, querymodification interferes with dynamic query caching because the modifiedqueries will no longer match the original text of the queries, whichmakes query matching problematic and impacts the performance benefits ofcaching.

Further, the solutions described above fail to address the requirementsfrom emerging privacy applications. Generally, a privacy policyindicates who can access what information, for what purpose, andresulting in what obligations. For example, a user John Doe may beallowed to access the credit card column from a customer table if he isusing the billing application to process a customer order, but he maynot be allowed to access that column for the purpose of sendingmarketing information to the customer. Existing FGAC solutions cannotaddress this requirement because they either do not support controllingaccess at the column level or they provide control access at the columnlevel, but only for columns that have been statically defined (i.e.,view-based techniques). Hence, a user is always restricted to a set ofcolumns, regardless of the purpose for which he or she is accessingthose columns.

Privacy applications are only one example where such flexibility isneeded. Recent user requirements in the area of database securityindicate that there is a need for database vendors to provide the notionof a session context. A session context is uniquely identified by a setof session attributes that may include the ID of the user whoestablished that session, the IP address of the computer from which theuser initiated the session, as well as other attributes as dictated by aparticular implementation or scenario. Within a particular context, auser can have one or more privileges on one or more database objectsthat are not necessarily available to them within a different context.Thus, it is only natural that the next logical user requirement would beto allow certain columns to be accessible within one context, but notwithin another context. Currently, the only way to accomplish this wouldbe to define a set of views that restrict access to certain columns andgrant access on those views to users depending on their session context.Maintaining several views, however, has the same drawbacks mentionedearlier.

Accordingly, there is a need for a flexible mechanism to control accessto elements in a database object based on one or more dynamicconditions, such as a session context or an access purpose withoutrequiring the creation and maintenance of static views or themodification of queries. The present invention addresses such a need.

SUMMARY OF THE INVENTION

A method, computer program product, and system for controlling access toelements in a database object are provided. In this document, a group ofone or more users is denoted as a user group and a set of one or more ofthe elements in a database object is denoted as an element set in thedatabase object. The method, computer program product, and systemprovide for receiving a request from a user to access the databaseobject, determining whether an access restriction is imposed on thedatabase object, the access restriction specifying a first user group towhich the access restriction is applicable, defining a first dynamiccondition the first user group must satisfy in order to access thedatabase object, and identifying a first element set in the databaseobject accessible to the first user group when the first dynamiccondition is satisfied, and controlling access to the elements in thedatabase object by the user based on the access restriction.

Controlling access to elements in a database object using accessrestrictions, rather than views or modified queries, eliminates theworries concerning the creation and maintenance of complex views, theusers bypassing restrictions by accessing underlying tables directly,the difficulties associated with routing user requests when there is alarge number of views, the ability to control access at both the row andcolumn level, the need to program strictly defined “predicate producing”procedures, and the problems of dynamic query caching interferences. Inaddition, because the access restrictions are defined using one or moredynamic conditions, the flexibility needed to address current privacyand security concerns is achieved.

Particular implementations can include controlling access to theelements in the database object by confirming whether the user is in thefirst user group when the access restriction is imposed on the databaseobject, verifying whether the user satisfies the first dynamic conditionwhen the user is in the first user group, and allowing the user toaccess the first element set when the user satisfies the first dynamiccondition.

Verifying whether the user satisfies the first dynamic condition mayinclude obtaining one or more session variables associated with the userwhen the user is in the first user group and comparing the one or moresession variable associated with the user to the first dynamic conditionto determine whether the user satisfies the first dynamic condition. Inan implementation, allowing the user to access the first element set inthe database object comprises generating a dynamic pseudo-view of thedatabase object comprising only the first element set in the databaseobject when the user satisfies the first dynamic condition andresponding to the request from the user using the dynamic pseudo-view ofthe database object.

In some embodiments, the database object is a table or a view, at leastone element in the first element set is a column, the first dynamiccondition is a session context or a session purpose associated with auser in the first user group, and the access restriction is stored in adatabase. Additionally, the access restriction can further define anadditional dynamic condition the first user group must satisfy in orderto access the first element set.

In other implementations, the access restriction further defines asecond dynamic condition the first user group must alternatively satisfyin order to access the database object and further identifies a secondelement set in the database object accessible to the first user groupwhen the second dynamic condition is satisfied. At least one element inthe first element set may also be an element in the second element set.

Further aspects may include determining whether another accessrestriction is imposed on the database object, the other accessrestriction specifying a second user group to which the other accessrestriction is applicable. The other access restriction can also defineanother dynamic condition the second user group must satisfy in order toaccess the database object and identify another element set in thedatabase object accessible to the second user group when the otherdynamic condition is satisfied. In one embodiment, at least one user inthe first user group is also a user in the second user group.

Another implementation also includes deciding whether an exception tothe access restriction is applicable to the user requesting access tothe database object and permitting the user to access the elements inthe database object when the exception to the access restriction isapplicable to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow of a method for controlling access to elementsin a database object according to an aspect of the invention.

FIG. 2 illustrates a system according to one embodiment of theinvention.

FIGS. 3-5 depict flowcharts of methods for controlling access toelements in a database object according to various implementations ofthe invention.

FIG. 6 shows a sample database object and exemplary dynamic pseudo-viewsgenerated based on the sample database object according to one aspect ofthe invention.

FIG. 7 is a block diagram of a data processing system with whichembodiments of the present invention can be implemented.

DETAILED DESCRIPTION

The present invention relates generally to database systems and moreparticularly to controlling access to elements in a database object. Thefollowing description is presented to enable one of ordinary skill inthe art to make and use the invention. Various modifications to thepreferred implementations and the generic principles and featuresdescribed herein will be readily apparent to those skilled in the art.Thus, the present invention is not intended to be limited to theimplementations shown, but is to be accorded the widest scope consistentwith the principles and features described herein.

FIG. 1 depicts a process 100 for controlling access to elements in adatabase object. At 102, a request to access the database object isreceived from a user. A determination is then made at 104 as to whetheran access restriction is imposed on the database object. In anembodiment, the access restriction specifies a first user groupcomprising one or more users to which the access restriction isapplicable, defines a first dynamic condition the first user group mustsatisfy in order to access the database object, and identifies a firstelement set comprising one or more of the elements in the databaseobject accessible to the first user group when the first dynamiccondition is satisfied. In this document, a group of one or more usersis denoted as a user group and a set of one or more of the elements in adatabase object is denoted as an element set in the database object.

Access to the elements in the database object by the user is controlledbased on the access restriction when the access restriction is imposedon the database object and the user is in the first user group (106). Insome implementations, the database object is a table or a view, at leastone element in the first element set is a column, and the first dynamiccondition is a session context or a session purpose associated with auser in the first user group.

A session purpose could be determined based on the type of applicationthe user is employing when requesting access to the database object, forexample, a purchasing application or a marketing application. A sessioncontext could be the location from which the user is requesting accessto the database object, for instance, from the office or at home. Thelocation may be determined based on the IP address of the computer fromwhich the user is requesting access.

Session context and session purpose are just two examples of dynamicconditions. A dynamic condition can also be a function. For example, thecondition can be “F (current time) is TRUE” where “F” is a function thatcompares the current time to the time of the day when access can begranted.

Illustrated in FIG. 2 is a system 200 including a server 202interconnected to clients 210-1 to 210-n via a network 208. Server 202and clients 210-1 to 210-n may be any data processing system, such ascomputers, workstations, and handheld portable devices. In addition,system 200 may include more or less clients in other embodiments.Network 208 may be the Internet or World Wide Web (WWW) in someimplementations.

System 200 also includes a database 204 and resources 206 a-206 b. Eachresource may be a storage media, a database, a set of XML (eXtensibleMarkup Language) documents, a directory service, such as LDAP(Lightweight Directory Access Protocol) server, or a backend system.Other embodiments of system 200 may include more or less databasesand/or resources.

Database 204 and resources 206 a-206 b are coupled to server 202. Theinterface between server 202 and database 204 and resources 206 a-206 bmay be a local area network, Internet, a proprietary interface, or anycombination of the foregoing. Clients 210-1 to 210-n can access database204 and resources 206 a-206 b through server 202. Any of server 202,database 204, resources 206 a-206 b, and clients 210-1 to 210-n may belocated remotely from one another or may share a location.

The configuration of system 200 is not intended as a limitation of thepresent invention, as will be understood by those of ordinary skill inthe art from a review of the following detailed description. Forexample, network 208 may comprise a wireless link, a telephonecommunication, a radio communication, or a computer network (e.g., aLocal Area Network (LAN) or a Wide Area Network (WAN)).

In one implementation, database 204 is operable to store a databaseobject comprising a plurality of elements and server 202 is operable toreceive a request from a user to access the database object. The requestmay be submitted by the user through one of clients 210-1 to 210-n.Server 202 is also operable to determine whether an access restrictionis imposed on the database object. The access restriction specifies afirst user group to which the access restriction is applicable, definesa first dynamic condition the first user group must satisfy in order toaccess the database object, and identifies a first element set in thedatabase object accessible to the first user group when the firstdynamic condition is satisfied.

Server 202 is then operable to control access to the elements in thedatabase object by the user based on the access restriction when theaccess restriction is imposed on the database object and the user is inthe first user group. In some embodiments, database 204 is furtheroperable to store the access restriction. The access restriction may bestored in a catalog of database 204 (not shown).

FIG. 3 shows a process 300 for controlling access to elements in thedatabase object according to an aspect of the invention. A request toaccess the database object is received from a user at 302. At 304, adetermination is made as to whether an access restriction is imposed onthe database object. The access restriction specifies a first user groupto which the access restriction is applicable, defines a first dynamiccondition and an additional dynamic condition the first user group mustsatisfy in order to access the database object, and identifies a firstelement set in the database object accessible to the first user groupwhen the first dynamic condition and the additional dynamic conditionare satisfied.

If no access restriction is imposed on the database object, the user ispermitted to access the elements in the database object (306). However,if the access restriction is imposed on the database object, process 300confirms whether the user is in the first user group to which the accessrestriction is applicable (308). When the user is not in the first usergroup, process 300 proceeds to 306 and the user is permitted to accessthe elements in the database object.

When the user is in the first user group, process 300 verifies whetherthe user satisfies the first dynamic condition (310). If the user doesnot satisfy the first dynamic condition, the user is prohibited fromaccessing the elements in the database object (312). If the user doessatisfy the first dynamic condition, process 300 verifies whether theuser satisfies the additional dynamic condition (314). When the userfails to satisfy the additional dynamic condition, process 300 proceedsto 312 and prohibits the user from accessing the elements in thedatabase object.

A dynamic pseudo-view of the database object comprising only the firstelement set is generated when the user satisfies the first dynamiccondition and the additional dynamic condition (316). The request fromthe user is then responded to using the dynamic pseudo-view of thedatabase object (318). A dynamic pseudo-view is a view-like entity withattributes similar to a predefined regular view. However, because it isdynamically created, it does not exist in a database, such as database204 in FIG. 2, and has no dependencies.

Depicted in FIG. 4 is another process 400 for controlling access toelements in a database object. At 402, a request is received from a userto access the database object. A determination is then made at 404 as towhether an access restriction is imposed on the database object. Theaccess restriction specifies a first user group to which the accessrestriction is applicable, defines a first dynamic condition the firstuser group must satisfy in order to access the database object, andidentifies a first element set in the database object accessible to thefirst user group when the first dynamic condition is satisfied.

In the embodiment, the access restriction also defines a second dynamiccondition the first user group must alternatively satisfy in order toaccess the database object and identifies a second element set in thedatabase object accessible to the first user group when the seconddynamic condition is satisfied. In some implementations, at least oneelement in the first element set is also an element in the secondelement set.

When no access restrictions are imposed on the database object, the useris permitted to access the elements in the database object (406). Whenthe access restriction is imposed on the database object, process 400confirms whether the user is in the first user group (408). If the useris not in the first user group, process 400 proceeds to 406 and permitsthe user to access the elements in the database object.

If the user is in the first user group, one or more session variablesassociated with the user is obtained (410). In one embodiment, when theuser establishes a session through some application, a session starttrigger will populate one or more session variables associated with theuser with the appropriate values based on information from the user andthe application. The session start trigger is a program that isautomatically executed when a session is established. Process 400 thencompares the one or more session variables associated with the user tothe first dynamic condition to determine whether the user satisfies thefirst dynamic condition (412).

The user is allowed to access the first element set in the databaseobject when the user satisfies the first dynamic condition, i.e., theone or more session variables match or correspond to the first dynamiccondition (414). When the one or more session variables do not match thefirst dynamic condition, process 400 compares them to the second dynamiccondition (416). If they also fail to match the second dynamiccondition, the user is prohibited from accessing the elements in thedatabase object (418). However, if the one or more session variablesassociated with the user match the second dynamic condition, the user isallowed to access the second element set in the database object (420).

FIG. 5 illustrates a process 500 for controlling access to elements in adatabase object according to a further embodiment of the invention. Arequest to access the database object is received from a user at 502. Adetermination is then made at 504 as to whether an access restrictionhas been imposed on the database object. The access restrictionspecifies a first user group to which the access restriction isapplicable, defines a first dynamic condition the first user group mustsatisfy in order to access the database object, and identifies a firstelement set in the database object accessible to the first user groupwhen the first dynamic condition is satisfied.

If no access restrictions are imposed on the database object, the useris permitted to access the elements in the database object (506). If,however, the access restriction has been imposed on the database object,process 500 decides whether an exception to the access restriction isapplicable to the user requesting access to the database object (508).When the exception to the access restriction is applicable to the userat block 508, a determination is made as to whether another accessrestriction is imposed on the database object, the other accessrestriction specifies a second user group to which the other accessrestriction is applicable (510). In an implementation, at least one userin the first user group is also a user in the second user group.

The other access restriction may further define another dynamiccondition the second user group must satisfy in order to access thedatabase object and identify another element set in the database objectaccessible to the second user group when the other dynamic condition issatisfied. Additionally, the other element set in the database objectmay be a subset of the first element set.

Process 500 will proceed to 506 to permit the user to access theelements in the database object when no other access restrictions areimposed on the database object. However, it will decide whether anexception to the other access restriction is applicable to the userrequesting access to the database object when the other accessrestriction is also imposed on the database object (512). The user ispermitted to access the elements in the database object if the exceptionto the other access restriction is applicable to the user (506). Incontrast, access to the elements in the database object by the user iscontrolled based on the other access restriction if the exception to theother access restriction is inapplicable to the user (514).

When the exception to the access restriction is not applicable to theuser at block 508, a determination is made as to whether another accessrestriction is imposed on the database object (516). If no other accessrestrictions are imposed on the database object, access to the elementsin the database object by the user is controlled based on the accessrestriction (518). However, if another access restriction is imposed onthe database object, process 500 will decide whether an exception to theother access restriction is applicable to the user requesting access tothe database object (520).

Access to the elements in the database object by the user will becontrolled based on the access restriction when the exception to theother access restriction is applicable to the user (518). Conversely,access to the elements in the database object by the user will becontrolled based on both access restrictions when the exception to theother access restriction is not applicable to the user (522).

Shown in FIG. 6 is a sample database object 600 with elements 602-610.Database object 600 is a table called “customer data” with a column 602for names, a column 604 for addresses, a column 606 for phone numbers,and a column 608 for credit card numbers. Table 600 has n number of rows610-1 to 610-n. Embodiments of the present invention enables accessrestrictions to be created such that it becomes possible to expresswhich elements 602-610 in database object 600 are accessible by a userand under what condition.

For example, suppose a user named “Bob” is allowed to access columns602, 604, and 608 in table 600 for the purpose of “Billing” and onlycolumns 602 and 604 for the purpose of “Marketing.” The followingStructured Query Language (SQL) statement illustrates how an accessrestriction can be created to limit user Bob's access to columns 602-610in table 600 based on the purpose of access.

-   -   CREATE RESTRICTION r1    -   ON TABLE customer data    -   FOR Bob    -   TO COLUMNS        -   (name, address, credit card) WHEN            (SessionVariablePurpose=‘Billing’)    -   (name, address) WHEN (SessionVariablePurpose=‘Marketing’)

Thus, when table 600 is queried by user Bob, server 202 in FIG. 2 forexample, can determine that an access restriction applies for user Bob.Server 202 may then look up a session variable “SessionVariablePurpose”associated with user Bob and read its value. If it is set to “Billing,”server 202 will implement access restriction “r1” in the query plan asif that restriction was statically defined as follows:

-   -   CREATE RESTRICTION r1    -   ON TABLE customer data    -   FOR Bob    -   TO COLUMNS (name, address, credit card)        A dynamic pseudo-view 612 a of table 600 that is depicted in        FIG. 6 can be generated to respond to user Bob's queries to        table 600.

However, if the value of the session variable “SessionVariablePurpose”was “Marketing,” then server 202 will implement restriction “r1” in thequery plan as if that restriction was statically defined as follows:

-   -   CREATE RESTRICTION r1    -   ON TABLE customer data    -   FOR Bob    -   TO COLUMNS (name, address)        A dynamic pseudo-view 612 b of table 600, which is illustrated        in FIG. 6, will be generated to respond to user Bob's queries on        table 600. For more information regarding the creation and use        of access restrictions, see “A Method for Implementing        Fine-Grained Access Control Using Access Restrictions,” U.S.        patent application Ser. No. 10/837,387, filed on Apr. 30, 2004,        which is hereby incorporated by reference in its entirety for        all purposes.

The invention can take the form of an entirely hardware embodiment, anentirely software embodiment, or an embodiment containing both hardwareand software elements. In one aspect, the invention is implemented insoftware, which includes, but is not limited to, firmware, residentsoftware, microcode, etc.

Furthermore, the invention can take the form of a computer programproduct accessible from a computer-usable or computer-readable mediumproviding program code for use by or in connection with a computer orany instruction execution system. For the purposes of this description,a computer-usable or computer-readable medium can be any apparatus thatcan contain, store, communicate, propagate, or transport the program foruse by or in connection with the instruction execution system,apparatus, or device.

The medium can be an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system (or apparatus or device) or apropagation medium. Examples of a computer-readable medium include asemiconductor or solid state memory, magnetic tape, a removable computerdiskette, a random access memory (RAM), a read-only memory (ROM), arigid magnetic disk, and an optical disk. Current examples of opticaldisks include DVD, compact disk-read-only memory (CD-ROM), and compactdisk-read/write (CD-R/W).

FIG. 7 depicts a data processing system 700 suitable for storing and/orexecuting program code. Data processing system 700 includes a processor702 coupled to memory elements 704 a-b through a system bus 706. Inother embodiments, data processing system 700 may include more than oneprocessor and each processor may be coupled directly or indirectly toone or more memory elements through a system bus.

Memory elements 704 a-b can include local memory employed during actualexecution of the program code, bulk storage, and cache memories thatprovide temporary storage of at least some program code in order toreduce the number of times the code must be retrieved from bulk storageduring execution. As shown, input/output or I/O devices 708 a-b(including, but not limited to, keyboards, displays, pointing devices,etc.) are coupled to data processing system 700. I/O devices 708 a-b maybe coupled to data processing system 700 directly or indirectly throughintervening I/O controllers (not shown).

In the embodiment, a network adapter 710 is coupled to data processingsystem 700 to enable data processing system 700 to become coupled toother data processing systems or remote printers or storage devicesthrough communication link 712. Communication link 712 can be a privateor public network. Modems, cable modems, and Ethernet cards are just afew of the currently available types of network adapters.

Various implementations for controlling access to elements in a databaseobject have been described. Nevertheless, one of ordinary skill in theart will readily recognize that various modifications may be made to theimplementations, and any variations would be within the spirit and scopeof the present invention. For example, the above-described process flowsare described with reference to a particular ordering of processactions. However, the ordering of many of the described process actionsmay be changed without affecting the scope or operation of theinvention. Accordingly, many modifications may be made by one ofordinary skill in the art without departing from the spirit and scope ofthe following claims.

1. A system comprising: a database operable to store a database object,the database object comprising elements; and a server coupled to thedatabase, the server comprising a processor and a memory, the serverbeing operable to: receive a request from a user to access the databaseobject; determine whether an access restriction is imposed on thedatabase object, the access restriction specifying a first user group towhich the access restriction is applicable, defining a first dynamiccondition the first user group must satisfy in order to access thedatabase object, wherein the first dynamic condition is a function thatcompares a current time to a time of the day when access can be granted,and identifying a first element set in the database object accessible tothe first user group when the first dynamic condition is satisfied; andcontrol access to the elements in the database object by the user basedon the access restriction, wherein controlling access to the elements inthe database object comprises: confirming whether the user is in thefirst user group when the access restriction is imposed on the databaseobject; verifying whether the user satisfies the first dynamic conditionwhen the user is in the first user group; and allowing the user toaccess the first element set when the user satisfies the first dynamiccondition, wherein allowing the user to access the first element setcomprises: generating a dynamic pseudo-view of the database objectcomprising only the first element set when the user satisfies the firstdynamic condition, wherein the dynamic pseudo-view is a view-like entitywith attributes similar to a predefined regular view, wherein thedynamic pseudo-view does not exist in a database, wherein the dynamicpseudo-view does not have dependencies; and responding to the requestfrom the user using the dynamic pseudo-view of the database object. 2.The system of claim 1 wherein the database object is a table or a view.3. The system of claim 1 wherein at least one element in the firstelement set is a column.
 4. The system of claim 1 wherein the firstdynamic condition is a session context or a session purpose associatedwith a user in the first user group.
 5. The system of claim 1 whereinthe server is further operable to: obtain one or more session variablesassociated with the user when the user is in the first user group; andcompare the one or more session variables associated with the user tothe first dynamic condition to determine whether the user satisfies thefirst dynamic condition.
 6. The system of claim 1 wherein the accessrestriction further defines a second dynamic condition the first usergroup must alternatively satisfy in order to access the database objectand further identifies a second element set in the database objectaccessible to the first user group when the second dynamic condition issatisfied.
 7. The system of claim 6 wherein at least one element in thefirst element set is also an element in the second element set.
 8. Thesystem of claim 1 wherein the access restriction further defines anadditional dynamic condition the first user group must satisfy in orderto access the first element set.
 9. The system of claim 1 wherein theserver is further operable to: determine whether another accessrestriction is imposed on the database object, the other accessrestriction specifying a second user group to which the other accessrestriction is applicable.
 10. The system of claim 9 wherein the otheraccess restriction further defines another dynamic condition the seconduser group must satisfy in order to access the database object andidentifies another element set in the database object accessible to thesecond user group when the other dynamic condition is satisfied.
 11. Thesystem of claim 10 wherein the other element set is a subset of thefirst element set.
 12. The system of claim 9 wherein at least one userin the first user group is also a user in the second user group.
 13. Thesystem of claim 1 wherein the server is further operable to: decidewhether an exception to the access restriction is applicable to the userrequesting access to the database object; and permit the user to accessthe elements in the database object when the exception to the accessrestriction is applicable to the user.
 14. A computer program productcomprising a computer-readable storage medium, the computer-readablestorage medium including a computer-readable program for controllingaccess to elements in a database object, wherein the computer-readableprogram when executed on a computer causes the computer to: receive arequest from a user to access the database object; determine whether anaccess restriction is imposed on the database object, the accessrestriction specifying a first user group to which the accessrestriction is applicable, defining a first dynamic condition the firstuser group must satisfy in order to access the database object, whereinthe first dynamic condition is a function that compares a current timeto a time of the day when access can be granted, and identifying a firstelement set in the database object accessible to the first user groupwhen the first dynamic condition is satisfied; and control access to theelements in the database object by the user based on the accessrestriction, wherein controlling access to the elements in the databaseobject comprises: confirming whether the user is in the first user groupwhen the access restriction is imposed on the database object; verifyingwhether the user satisfies the first dynamic condition when the user isin the first user group; and allowing the user to access the firstelement set when the user satisfies the first dynamic condition, whereinallowing the user to access the first element set comprises: generatinga dynamic pseudo-view of the database object comprising only the firstelement set when the user satisfies the first dynamic condition, whereinthe dynamic pseudo-view is a view-like entity with attributes similar toa predefined regular view, wherein the dynamic pseudo-view does notexist in a database, wherein the dynamic pseudo-view does not havedependencies; and responding to the request from the user using thedynamic pseudo-view of the database object.
 15. The computer programproduct of claim 14 wherein the database object is a table or a view.16. The computer program product of claim 14 wherein at least oneelement in the first element set is a column.
 17. The computer programproduct of claim 14 wherein the first dynamic condition is a sessioncontext or a session purpose associated with a user in the first usergroup.
 18. The computer program product of claim 14 wherein verifyingwhether the user satisfies the first dynamic condition comprises:obtaining one or more session variables associated with the user whenthe user is in the first user group; and comparing the one or moresession variables associated with the user to the first dynamiccondition to determine whether the user satisfies the first dynamiccondition.
 19. The computer program product of claim 14 wherein theaccess restriction further defines a second dynamic condition the firstuser group must alternatively satisfy in order to access the databaseobject and further identifies a second element set in the databaseobject accessible to the first user group when the second dynamiccondition is satisfied.
 20. The computer program product of claim 14wherein at least one element in the first element set is also an elementin the second element set.